Various surgical procedures rely on placement of electrodes into the body (e.g., electrode devices, electrode-bearing leads or catheters, etc.). For example, a typical implantable cardiac defibrillator (ICD) includes a “can” for placement in a pectoral pocket and an electrode-bearing lead for placement into a chamber of the heart or a vein of the heart. In this example, an electrode of the can and an electrode of the lead can sense cardiac electrical activity indicative of fibrillation and respond (e.g., by control logic in the can) by delivering energy to defibrillate the heart. To ensure proper performance, whether for sensing or for defibrillating, stability of the can and stability of the lead are beneficial.
In another example, where a patient is treated by a cardiac resynchronization therapy (CRT) device that relies on biventricular pacing, an electrode-bearing lead may be placed into the right ventricle and another electrode-bearing lead may be placed in a vein of a wall of the left ventricle. As the algorithms for delivery of such therapy become more complex, accurate sensing becomes more important as does an ability to accurately and reproducibly deliver pacing stimuli. In this example, stability of sensing and pacing electrodes becomes quite important.
In either example, where an electrode or lead lacks stability or dislodges, depending on the severity, surgery may be required to remedy the issue. Alternatively, if the lack of stability or the dislodgement is tolerated, a device's ability to delivery therapy in an optimal manner may be compromised (e.g., an electrode configuration for sensing may become unreliable to support an algorithm such as for automatic determination of capture threshold).
While many leads include anchoring mechanisms, such mechanisms do not guarantee stability. However, if a lead can be placed in a stable location or a location of known stability, a clinician can predict better possible outcomes and even longevity of an implantable therapy device. As to the latter, data indicates that an unstable electrode is likely to trigger algorithms such as an automatic capture threshold determination algorithm, which, in turn, can consume precious resources (e.g., consider a battery as an implantable device's limited power supply).
While ICD and CRT have been mentioned, electrode and lead stability can be an issue with other investigations or procedures. For example, consider an ablation procedure in a region of the heart that may be accessed via two different catheter paths. If one of the paths proves for more stable placement of an ablation instrument (e.g., electrode, RF, chemical, etc.), the clinician may perform the procedure with less risk and perhaps a better clinical outcome. In another example, consider nerve or tissue stimulation therapies such as those for vagal nerve stimulation or for diaphragm stimulation. These therapies can benefit from known, trackable or otherwise quantifiable stability metrics. In yet another example, consider placement of a sensor in the body that may require stability for suitable signal-to-noise.
As described herein, various exemplary techniques can assess stability in acute states and optionally chronic states. As explained, such stability information can be beneficial in aiding a clinician to make decisions regarding an investigation or a therapy.